Assignment Lab

ENGR 200: Materials of Engineering

Laboratory 3

Tensile Test I.

OBJECTIVES

The purpose of this experiment is to familiarize the students with performing tension tests and obtaining the strength and ductility values from the test results of several metals. The tensile properties of these metals will be contrasted, and the properties will be compared with those in reference books.

II.INTRODUCTION

The tensile test is the primary test used in determining the mechanical properties of materials. From this test, it is possible to determine the yield strength, tensile strength, modulus of elasticity, and ductility of a given material. This type of data is essential for mechanical and structural designs and is usually compiled in materials handbooks for commercially available materials.

III. EXPERIMENTAL

Materials and Apparatus

• Instron Tensile Test System (Series 3369, Figure 1) • Extensometer • Four tension tests specimens – aluminum (2024 –T4), copper (C 11000), brass (C36000), and

steel (1010 cold-rolled) (see Figure 2) • Vernier caliper

 

Aluminum (2024 –T4)

Steel (1010 cold-rolled)

Brass (C36000)

Copper (C 11000)

 

Figure  1:  Instron  Tensile  Test   Machine,  Series  3369   Figure  2:  Tensile  Test  specimens.

 

 

 

Figure 3: Tensile Test Specimen

Experimental Procedure

1) 4 groups will test 1 specimen each, which is made of one of the following metals: aluminum (2024 –T4), copper (C 11000), brass (C36000), and steel (1010 cold-rolled)

2) Prior to testing, measure and label the specimens’ dimensions, and record them in your data sheet.

You may also digitally photograph the specimen.

3) Test procedure:

Turn on the machine and let it warm up for 15 minutes before performing any test.

a) Specimen preparation

• Mark a 2’” (50.8 mm) gage length within the center portion of the specimen using a marker pen. (see Figure 3 for the location of the gage length)

b) Attach specimen to grip assembly

 

• Mount the specimen to the upper grip assembly and allow it to hang freely. This is to minimize side loading or bending moment created in the specimen.

• Make sure the faces of the grip cover the entire area to be gripped; otherwise your specimen may

slip or even break inside the gripped area (“jaw break”). Tighten the clamp.

• Repeat the same procedure for the lower grip assembly, and tighten the lower clamp

c) Set up test program

Check to ensure that these parameters are entered accurately in the right fields:

-Gage length – Sample thickness – Ambient temperature

 

 

d) Testing

• Zero out all the load and strain values on the specimen as shown on the screen • Begin the test – the cross-head will begin to move at a pre-determined speed • When the pre-set strain value is reached and the cross – head stop moving, remove the

extensometer. • Continue the test until the sample begins to neck and finally raptures (breaks). Note the specimen

temperature at which this occurs. • Carefully remove the fractured samples.

4) Use the Vernier caliper to measure the following dimensions of the fractured sample:

-­‐ Gage length (Note: put the fractured sample back together and measure the distance between

your original marking) -­‐ Width (of fractured surface) -­‐ Thickness (of fractured surface)

 

5) Photograph the fractured specimens-top view and side view. Pay particular attention to the fractured region. Include these photos in your Appendices section.

6) Photograph the fractured surface (oblique view). Include these sketches (and photos) in your

Appendices section.

7) Computer generated data for all four test specimens will be available in Excel format and distributed to the class after the lab session. These data will be used to

-locate the yield stress -locate the tensile stress -locate the fracture load -compute ductility of the specimen

Note: If you are not familiar with data manipulation and graphing using Microsoft Excel, please inform your Lab Instructor ASAP.

 

IV. DELIVERABLES FROM YOU

1. Submit your Tech Memo as a PDF file on designated date (see ENGR 200 syllabus) to your Instructor. Hardcopy is NOT required. Please note that each student is required to submit his/her own Tech Memo (group discussion is allowed; however, you should write your own Tech Memo).

Please include the following two sections in your memo:

i) Introduction (1/2 page): Discuss “What is a tensile test, its purpose and significance, the materials tested, what material properties can we obtain from this test, why are these properties important.

 

 

ii) Results and Discussion (2.5 pages): Discuss results and observations based on the tables, figures, and photos you prepared. Please provide insights, don’t just regurgitate numbers. E.g. don’t just write “Based on Figure 1 and 2, the Young Modulus of steel and copper are 100GPa and 50GPa, respectively”, instead write “Based on Figure 1 and 2, the Young Modulus of steel and copper are 100GPa and 50GPa, respectively. Therefore, steel is twice stiffer than copper and under similar tensile loads; copper will elongate twice as much as steel.

Please** attach tables, figures and photos in the Appendices**

1. Please include and discuss the following in your memo:

a) From specimen dimension measurements construct Table 1, for initial and final areas and change in the gage length for the four specimens.

b) From Table 1, calculate the ductility from the initial and final dimensions of the specimen, i.e.

based on i) percent elongation and ii) percent reduction in area. Present the results in Table 2.

c) Using computer data, present stress vs. strain diagrams for the four materials. Label these graphs as, e.g. Figure 4, Figure 5, Figure 6 and Figure 7.

d) Using computer data, construct Table 3, comparison of Young’s Moduli values for the four

materials and those obtained from the textbook (Appendix B).

e) From computer data, construct Table 4, comparison of yield and ultimate tensile strength values for the four materials and those obtained from the textbook (Appendix B).

2. On your memo, please also include your team members’ names.

 

 

 

ENGR 200: Materials of Engineering

Laboratory 3

Data Sheet for Tensile Test

Name:

Group Members:

Date:

1. Photo of specimens: Please, include the following photos in your Appendix section.

a) Specimens after test –top view & side view b) Specimens’ fractured surfaces – oblique view of both surfaces.

Table 1: Data Collection:

Material Initial

Thickness [mm]

Initial Width [mm]

Initial Area [mm2]

Initial Gage Length [mm]

Final Thickness [mm]

Final Width [mm]

Final Area [mm2]

Final Gage Length [mm]

 

APPENDIX B: 1 (a) Specimen Top and Side Views (After Test)

Steel Specimen (Top View and Side View)

Top

 

 

Side

Brass Specimen (Top View and Side View)

 

 

Top

 

Side

Aluminum Specimen (Top View and Side View)

Top

 

Side

Copper Specimen (Top View and Side View)

Top

 

 

Side

 

1(b) Specimen’s Fractured Surfaces (Oblique Views of Both Surfaces) (Please dimension and label sketches)

 

Steel Specimen (Oblique View)

 

Brass specimen (Oblique View)

 

 

 

 

Aluminum specimen (Oblique View)

 

 

Copper specimen (Oblique view)

 

Text Book reference W.D Callister, Jr. and D.G Rethwisch.Materials Science and Engineering, An introduction. 9th ed,. John Wiley & Sons, Inc,. 2014

 

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